This invention is related to the detection of air turbulence and more specifically, to a method and system for determining air turbulence using bi-static measurements.
In air travel, the most hazardous phase that an aircraft experiences is the landing or takeoff. In these phases, an aircraft is vulnerable to unexpected changes in the surrounding environment. For example, wind shears or other sudden or violent changes in the direction of the wind can cause a misalignment of the aircraft with respect to the runway. Furthermore, sudden drops in air pressure can cause the aircraft to suddenly lose altitude at a time when excess altitude is not available.
In addition to natural changes in the surrounding environment, aircraft landings and takeoffs also create vortexes or wake disturbances in the environment behind the aircraft that may affect the operation of a next and subsequent aircraft. Minimum required distances between aircraft have been established in order to reduce the effects of the vortex on the next or subsequent aircraft, hence, improving their safety However, such required minimum distances are set to accommodate worst-case conditions and are longer than necessary.
Knowledge of the disturbances or turbulence in the aircraft""s surrounding environment can be used to improve aircraft safety and can also be used to reduce the minimum distance needed between aircraft, thus, increasing airport efficiency.
Hence, there is a need for determining disturbances or turbulence in the atmosphere surrounding an aircraft. In one aspect, knowledge of wake disturbances in the area around the ends of aircraft runways is important. In another aspect, knowledge of wake disturbance immediately ahead of an aircraft is similarly important.
A method for determining atmospheric disturbances or turbulence preceding an aircraft or induced by an aircraft is disclosed. The method includes receiving a signal from a plurality of sensor arrays, each including at least one sensor element, distributed in a predetermined manner. Each of the sensor elements is in communication with a corresponding receiving system that is operable to receive and process electromagnetic energy that is emanating from an approaching or departing aircraft. A determination is then made regarding air or wake turbulence by determining a rate of change of signal phase among selected sets of signals received at the receiving systems. A turbulence map is then determined from the determined rate of change of the phase and the angle of the received signal. When the rate of phase change exceeds known levels an indication of turbulence is made. In another aspect of the invention, each of the sensor arrays can include a plurality of sensor elements, which may be used to determine a precise angle of arrival of the received signal. In still another aspect of the invention, sensor arrays may be located on-board an aircraft to monitor turbulence immediately before it.